Protection of electrical devices with voltage variable materials

ABSTRACT

An arrangement of voltage variable materials for the protection of electrical components from electrical overstress (EOS) transients. A device having a plurality of electrical leads, a ground plane and a layer of voltage variable material. The voltage variable material physically bonds the plurality of electrical leads to one another as well as provides an electrical connection between the plurality of electrical leads and the ground plane. A die having a circuit integrated therein is attached to the ground plane. Conductive members electrically connect the plurality of electrical leads to the integrated circuit. At normal operating voltages, the voltage variable material has a high resistance, thus channeling current from the electrical leads to the integrated circuit via the conductive members. In response to a high voltage EOS transient, the voltage variable material essentially instantaneously switches to a low resistance state, channeling the potentially harmful EOS transient to the ground plane and away from the integrated circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/097,314 filed on Aug. 20, 1998, the disclosure ofwhich is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention generally relates to the use of voltagevariable materials for the protection of electronic components againstelectrical overstress (EOS) transients.

BACKGROUND OF THE INVENTION

[0003] There is an increased demand for materials and electricalcomponents which can protect electronic circuits from EOS transientswhich produce high electric fields and usually high peak powers capableof destroying circuits or the highly sensitive electrical components inthe circuits, rendering the circuits and the components nonfunctional,either temporarily or permanently. The EOS transient can includetransient voltage or current conditions capable of interrupting circuitoperation or destroying the circuit outright. Particularly, EOStransients may arise, for example, from an electromagnetic pulse, anelectrostatic discharge, lightening, or be induced by the operation ofother electronic or electrical components. Such transients may rise totheir maximum amplitudes in microsecond to subnanosecond time frames andmay be repetitive in nature. A typical waveform of an electricaloverstress transient is illustrated in FIG. 1. The peak amplitude of theelectrostatic discharge (ESD) transient wave may exceed 25,000 voltswith currents of more than 100 amperes. There exist several standardswhich define the waveform of the EOS transient. These include IEC1000-4-2, ANSI guidelines on ESD (ANSI C63.16), DO-160, and FAA-20-136.There also exist military standards, such as MIL STD 461 and MIL STD 883part 3015.

[0004] Materials for the protection against EOS transients (EOSmaterials) are designed to respond essentially instantaneously (i.e.,ideally before the transient wave reaches its peak) to reduce thetransmitted voltage to a much lower value and clamp the voltage at thelower value for the duration of the EOS transient. EOS materials arecharacterized by high electrical resistance values at low or normaloperating voltages and currents. In response to an EOS transient, thematerial switches essentially instantaneously to a low electricalresistance value. When the EOS threat has been mitigated these materialsreturn to their high resistance value. These materials are capable ofrepeated switching between the high and low resistance states, allowingcircuit protection against multiple EOS events. EOS materials are alsocapable of recovering essentially instantaneously to their original highresistance value upon termination of the EOS transient. For purposes ofthis application, the high resistance state will be referred to as the“off-state” and the low resistance state will be referred to as the“on-state.” FIG. 2 illustrates a typical electrical resistance versusd.c. voltage relationship for EOS materials. Circuit componentsincluding EOS materials can shunt a portion of the excessive voltage orcurrent due to the EOS transient to ground, thus, protecting theelectrical circuit and its components. The major portion of the threattransient is reflected back towards the source of the threat. Thereflected wave is either attenuated by the source, radiated away, orre-directed back to the surge protection device which responds with eachreturn pulse until the threat energy is reduced to safe levels.

[0005] In particular, the present invention is directed to theapplication of voltage variable materials to electrical devices toprovide protection against EOS transients.

[0006] Accordingly, any of the following EOS materials and methods formaking EOS materials can be used in the present invention, thedisclosures of which are incorporated herein by reference.

[0007] U.S. Provisional Patent Application No. 60/064,963 disclosescompositions for providing protection against EOS. The compositionsinclude a matrix formed of a mixture of an insulating binder, conductiveparticles having an average particle size of less than 10 microns, andsemiconductive particles having an average particle size of less than 10microns. The compositions utilizing relatively small particle sizedconductive and semiconductive fillers exhibit clamping voltages in arange of about 30 volts to about 2,000 volts or greater.

[0008] U.S. Pat. No. 2,273,704, issued to Grisdale, discloses granularcomposites which exhibit non-linear current voltage relationships. Thesemixtures are comprised of granules of conductive and semiconductivegranules that are coated with a thin insulative layer and are compressedand bonded together to provide a coherent body.

[0009] U.S. Pat. No. 2,796,505, issued to Bocciarelli, discloses anon-linear voltage regulating element. The element is comprised ofconductor particles having insulative oxide surface coatings that arebound in a matrix. The particles are irregular in shape and make pointcontact with one another.

[0010] U.S. Pat. No. 4,726,991, issued to Hyatt et al., discloses an EOSprotection material comprised of a mixture of conductive andsemiconductive particles, all of whose surfaces are coated with aninsulative oxide film. These particles are bound together in aninsulative binder. The coated particles are preferably in point contactwith each other and conduct preferentially in a quantum mechanicaltunneling mode.

[0011] U.S. Pat. No. 5,476,714, issued to Hyatt, discloses EOS compositematerials comprised of mixtures of conductor and semiconductor particlesin the 10 to 100 micron range with a minimum proportion of 100 angstromrange insulative particles, bonded together in a insulative binder. Thisinvention includes a grading of particle sizes such that the compositioncauses the particles to take a preferential relationship to each other.

[0012] U.S. Pat. No. 5,260,848, issued to Childers, discloses foldbackswitching materials which provide protection from transientovervoltages. These materials are comprised of mixtures of conductiveparticles in the 10 to 200 micron range. Semiconductor and insulativeparticles are also employed in these compositions. The spacing betweenconductive particles is at least 1000 angstroms.

[0013] Additional EOS polymer composite materials are also disclosed inU.S. Pat. Nos. 4,331,948, 4,726,991, 4,977,357, 4,992,333, 5,142,263,5,189,387, 5,294,374, 5,476,714, 5,669,381, and 5,781,395, the teachingsof which are specifically incorporated herein by reference.

SUMMARY OF THE INVENTION

[0014] It is an object of the present invention to apply voltagevariable materials to numerous different configurations of electricaldevices to provide protection from EOS transients. In a first embodimentof the present invention, an electrical device (e.g., a chip comprisingan integrated circuit) comprises a plurality of electrical leads, aground plane and a layer of voltage variable material. Each electricallead is spaced apart from the other electrical leads and the groundplane. The layer of voltage variable material fills the spacing betweenthe electrical leads and the ground plane, physically connecting theelectrical leads and the ground plane.

[0015] The device can be manufactured by providing a lead frame having aplurality of electrical leads and a ground plane. There is apredetermined spacing, A, between each electrical lead and apredetermined spacing, B, between each lead and the ground plane. Avoltage variable material is applied to the lead frame such that thematerial fills the spacing, A, between the leads and the spacing, B,between each lead and the ground plane. The voltage variable materialphysically connects the plurality of leads to the ground plane. A die orintegrated circuit is mounted on the ground plane. The leads are thenelectrically connected to the integrated circuit. The plurality ofelectrical leads, ground plane and die are encapsulated in a protectivecoating leaving a portion of the plurality of leads exposed. The exposedportion of the leads are then formed into connector pins. The advantageof such a device and method is: (1) the need for a separate substrate toaccommodate the voltage variable material, electrical leads, groundplane and die is eliminated; (2) protection from EOS transients is builtinto the existing structure of the electrical device, thus, conservingreal estate on a printed circuit board; and (3) the voltage variablematerial can be applied to a variety of device configurations.

[0016] In another embodiment of the present invention, the voltagevariable material forms a tape upon which a circuit is built up to formthe electrical device. Starting with a layer of voltage variablematerial, a first electrode is attached to a first side of the layer anda second electrode is attached to a second side of the layer. Theelectrodes can be a metal foil or a metal layer attached by anyconventional method (e.g., lamination, electroless plating, electrolyticplating, vapor deposition). The electrodes are then processed bymasking/etching or photo lithographic methods (as disclosed in U.S. Pat.No. 5,699,607 and incorporated herein by reference) to form a laminatecomprised of a ground plane and a plurality of electrical leads on thelayer of voltage variable material. The layer of voltage variablematerial is then cured and pressure is applied to the laminate to formthe final integrated tape device. In order to provide mechanicalstability to the device during the processing of the electrodes, thevoltage variable material may be cured prior to the step of processingthe electrodes.

[0017] In yet another embodiment of the present invention, a hybrid tapeof voltage variable material is simply bonded to an existing lead frameto provide protection against EOS transients. The lead frame includes aplurality of electrical leads electrically connected to die having acircuit integrated therein. The die is attached to a conductive dieconnector plate. The hybrid tape is comprised of a layer of voltagevariable material with a first conductive layer disposed on one sidethereof. The other side of the layer of voltage variable material isbonded to the lead frame, physically connecting the plurality ofelectrical leads to the die connector plate. The plurality of electricalleads are then trimmed from the lead frame to produce the electricaldevice.

[0018] In a further embodiment of the present invention, a layer ofvoltage variable material has a conductive adhesive applied to a firstside. The adhesive has a anisotropic voltage breakdown. A conductivelayer (e.g., metal foil or electroless layer of copper) is applied to asecond side of the layer of voltage variable material to form a tape.Preferably, the conductive adhesive collapses to a very thin layer whenbonded to an object (e.g, a lead frame or pin-style electricalconnection of an electrical device to a trace on a printed circuitboard).

[0019] In still another embodiment of the present invention, theelectrical device comprises a hollow conductive tube having a layer ofvoltage variable material disposed on the outer surface thereof. Theelectrical device is especially well suited for providing protectionbetween the electrical leads of a connector housing. The device isplaced between a first set of a plurality of electrical leads and asecond set of a plurality of electrical leads, with the layer of voltagevariable material contacting both the first and second sets of pluralityof leads and the conductive tube being electrically grounded.

[0020] In another embodiment of the present invention, an integratedcircuit is encapsulated in a protective housing comprised of a voltagevariable material. The protective housing bonds the individualcomponents of the circuit together, protects the integrated circuit fromundesired external influences (mechanical and electrical), andelectrically protects the integrated circuit from EOS transients.

[0021] In a final embodiment of the present invention, the housing of anelectrical connector is composed of a voltage variable material. Thematerial is applied between the electrical connectors to which an EOStransient may be applied and the ground reference of the electricalconnectors.

[0022] Other advantages and aspects of the present invention will becomeapparent upon reading the following description of the drawings anddetailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 graphically illustrates a typical current waveform of anEOS transient.

[0024]FIG. 2 graphically illustrates the electrical resistance versusd.c. voltage relationship of typical EOS materials.

[0025]FIG. 3 illustrates a typical lead frame utilized in themanufacture of integrated circuits.

[0026]FIG. 4 illustrates a portion of the lead frame illustrated in FIG.3 with a voltage variable material laminated to fill the spacing betweenthe plurality of electrical leads and the ground plane.

[0027]FIG. 5 illustrates a cross-sectional view of an electrical deviceaccording to one embodiment of the present invention.

[0028] FIGS. 6A-6D illustrate various steps for manufacturing anelectrical device according to another embodiment of the presentinvention.

[0029]FIG. 7 illustrates an alternative embodiment of the electricaldevice shown in FIGS. 6A-6D.

[0030] FIGS. 8A-8B illustrate a voltage variable tape and theapplication of the tape to an electrical device to provide protectionagainst EOS transients.

[0031]FIG. 9A illustrates the voltage variable tape of FIG. 8A with aconductive adhesive applied to one side.

[0032]FIG. 9B illustrates the anisotropic voltage breakdowncharacteristics of the conductive adhesive illustrated in FIG. 9A.

[0033]FIG. 10 illustrates the application of the voltage variable tapeof either FIGS. 8A or 9A applied to a pin-style electrical connection ofan electrical device to a conductive trace on a printed circuit board.

[0034]FIG. 11 illustrates a connector housing mounted on a printedcircuit board.

[0035]FIG. 12 illustrates the tape of FIG. 8A in the shape of a tubeinserted between the connectors in the connector housing of FIG. 11 toprovide protection against EOS transients.

[0036]FIG. 13 illustrates an electrical device, e.g., an integratedcircuit similar to that illustrated in FIG. 5, encapsulated in a voltagevariable housing.

[0037]FIG. 14 is a schematic diagram illustrating the electricalrelationship between the voltage variable material and the electricaldevice or circuit to be protected from EOS transients.

[0038]FIG. 15 illustrates an electrical connector housing formed from avoltage variable material.

DETAILED DESCRIPTION OF THE INVENTION

[0039] While this invention is susceptible of embodiment in manydifferent forms, there is shown in the drawings and will herein bedescribed in detail a preferred embodiment of the invention with theunderstanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the broad aspect of the invention to the embodimentsillustrated.

[0040] Referring to FIG. 14, it should be understood by those ofordinary skill in the art that in the present invention, voltagevariable materials 10 shall be applied between the conductor 20 to whichthe EOS transient may be applied and the ground reference 30 of theconductor 20.

[0041] With reference now to FIGS. 3-5, a voltage variable material 10is applied to a lead frame 50 comprised of a plurality of electricalleads 60, 60′ 61, 61′ 62, 62∝ 63, 63′ 64, 64′ . . . (60, 60′, etc.) anda ground plane 70. Each electrical lead is spaced apart from the otherelectrical leads by a predetermined dimension A. The ground plane 70 isadjacent to and spaced apart from corresponding electrical leads 60,60′, etc. (e.g., ground plane 70 is interposed between leads 60 and 60′)by a predetermined dimension B. A layer of voltage variable material 10fills the space between the plurality of electrical leads 60, 60′, etc.,and the space between the plurality of electrical leads 60, 60′, etc.and the ground plane 70. The layer of voltage variable material 10physically connects the leads to the ground plane 70.

[0042] As shown in FIG. 5, a die or chip having an electrical circuitintegrated therein (as is commonly known in the art) 80 is attached tothe ground plane 70.

[0043] Conductive members 90 (e.g., wires, conductive traces)electrically connect the plurality of leads 60, 60′, etc. to theintegrated circuit. In a preferred embodiment (not shown) the pluralityof electrical leads 60, 60′, etc., the ground plane 70, integratedcircuit 80 and conductive members 90 are encapsulated in a protective,preferably insulative, housing. A portion of each of the plurality ofelectrical leads 60, 60′, etc. is exposed from the protective housing,i.e., extend outwardly from the protective housing, and form a pluralityof connector pins 160,160′, 161,161′, 162,162′ . . . etc. (See FIG. 13wherein the protective housing 170 is formed from a voltage variablematerial 10).

[0044] In one embodiment of the present invention, the predetermineddimension, A, (i.e., the spacing between each of the plurality ofelectrical leads) is greater than the predetermined dimension, B, (i.e.,the spacing between each of the plurality of electrical leads and theground plane). Thus, when an EOS transient is applied to the electricalleads 60, 60′, etc. and the voltage variable material 10 switches to itslow resistance “on-state,” the resistance of the material 10 in thedirection between the leads 60, 60′, etc. and the ground plane 70 willbe less than the resistance of the material 10 in the direction betweenthe electrical leads 60, 60′, etc. Accordingly, the EOS transient willbe channeled to the ground plane 70, and away from the integratedcircuit 80.

[0045] The electrical device illustrated in FIGS. 3-5 is manufactured byproviding a lead frame 50 having a plurality of electrical leads 60,60′, etc. and a ground plane 70.

[0046] As discussed above, there is a predetermined spacing, A, betweenthe leads 60, 60′, etc. and a predetermined spacing, B, between theleads 60, 60′, etc. and the ground plane 70. A voltage variable material10 is applied to lead frame 50, physically connecting the plurality ofelectrical leads 60, 60′, etc. to the ground plane 70. Preferably, thevoltage variable material 10 is applied to the lead frame 50 bylaminating a thin film of the material 10 on the lead frame 50.Alternatively, the material 10 may be applied by any conventional method(e.g., brushing, spraying, extruding). As shown in FIG. 4, during thelamination process the voltage variable material 10 fills the spacing,A, between the electrical leads 60, 60′, etc. and the spacing, B,between the electrical leads 60, 60′, etc. and the ground plane 70. Adie or chip having electronic circuitry (e.g., integrated circuit or adiscrete electronic component) 80 electrically connected thereto isattached to the ground plane 70. The die or chip 80 can be attached tothe ground plane 70 before or after the lamination step. It ispreferred, however, to attach the die or chip 80 to the ground plane 70after the lamination step since the layer of voltage variable material10 increases the structural integrity of the device, making the deviceeasier to process.

[0047] The plurality of electrical leads 60, 60′, etc. are electricallyconnected, preferably by wire bonding 90, to the electronic circuitry onthe die or chip 80. In the next step, the plurality of electrical leads60, 60′, etc. and the ground plane 70 are removed or trimmed from thelead frame 50 to form the electrical device. Preferably, the electricaldevice is encapsulated in a protective, insulative housing, leaving aportion of the leads exposed. Finally, the exposed portions of the leadsare formed into a plurality of connector pins for electricallyconnecting the device to a power supply.

[0048] Referring to FIGS. 6A-6D, an electrical device according toanother embodiment of the present invention may be made by forming acircuit directly on the surface of a thin film or tape-likeconfiguration of voltage variable material 10.

[0049] Initial first and second electrodes 95, 100 are attached to firstand second surfaces of the material 10. The electrodes 95, 100 may becomposed of a metallic foil or a conductive layer (e.g., silver orcopper plating). Portions of the electrodes 95, 100 are masked and theexposed portions of the electrodes are etched away, leaving behind thedesired lead and ground plane 70 geometry. Alternatively, the desiredcircuit geometry may be formed by applying a photo-imagable material tothe electrodes 95, 100, applying a photo resist material in a desiredpattern, developing the photo resist material, removing thenon-developed photo resist material, and etching away the exposedportions of the electrodes 95, 100 to create a plurality of electricalleads 60, 60′, etc. and a ground plane 70 on the voltage variablematerial 10 (See FIG. 6D). This process is more fully described in U.S.Pat. No. 5,669,607, the teaching of which is incorporated herein byreference.

[0050] The voltage variable material 10 is then cured. Pressure is thanapplied to the laminate (i.e., the layer of voltage variable material 10with the leads 60, 60′, etc. and ground plane 70 formed on either: (i)the first surface of the voltage variable material 10; (ii) the secondsurface of the voltage variable material 10; or, (iii) both the firstand second surfaces of the voltage variable material 10) so that thevoltage variable material fills the areas between the leads 60, 60′,etc. and the ground plane 70 where portions of the electrode have beenremoved. FIGS. 6A-6D illustrate the embodiment wherein the leads 60,60′, etc. and the ground plane have been formed on both the first andsecond surfaces of the voltage variable material 10. As a result of thepressure applied to the voltage variable material 10, the material 10fills the spacing, A, (i.e., the spacing between the plurality of leads60, 60′, etc.) and the spacing, B, (i.e., the spacing between the leads60, 60′, etc. and the ground plane 70). The curing and pressurizingsteps may be accomplished in a single step by placing the laminate in aheated press.

[0051] In an alternative embodiment to the device disclosed in FIGS.6A-6D, a discrete, surface-mountable device is illustrated in FIG. 7. Afirst conductive layer forms a ground plane 70 on a first surface of thevoltage variable material 10. First and second conductive terminal pads110, 120 are disposed on a second surface of the voltage variablematerial 10. A die having electrical circuitry attached thereto 80 iselectrically connected to the first and second conductive terminal pads110, 120. As shown in FIG. 7, the conductive terminal pads 110, 120 canbe electrically connected via solder or the like to a trace on aconventional printed circuit board.

[0052] Referring now to FIGS. 8A-8B, in another embodiment of thevoltage variable tape-like configuration illustrated in FIGS. 6A-6D, aconductive layer 100 is applied to a first surface of the thin filmvoltage variable material 10 to form the tape. The opposite surface ofthe voltage variable material 10 is bonded to a lead frame 50 comprisinga plurality of electrical leads 60, 60′, etc. a ground plane 70 and adie or chip having electronic circuitry attached thereto 80. The voltagevariable material 10 physically connects the ground plane 70 and theplurality of electrical leads 60, 60′, etc. The leads 60, 60′, etc. inturn are electrically connected to the circuitry attached to the die 80by conductive members 90.

[0053] Yet another embodiment of the voltage variable tape-likeconfiguration is disclosed in FIGS. 9A, 9B and 10. A conductive adhesive130 is applied to one surface of the voltage variable material 10. Aconductive layer 100 is applied to a second surface of the material 10.The conductive adhesive 130 has an anisotropic voltage breakdown. Withreference to FIG. 9B, the voltage breakdown, V_(B), of the conductiveadhesive 130 measured in the direction of potential current flow throughthe conductive adhesive 130 (in most applications generallyperpendicular to the layer of voltage variable material 10, e.g.,V_(BY)) is less than the voltage breakdown measured in any otherdirection (e.g., V_(BZ) or V_(BX)). When bonded to an object, forexample a lead frame 50 or a pin-style connector 180 on a printedcircuit board, the conductive adhesive 130 collapses to a very thinlayer. FIG. 10 illustrates a tape 170 having such a conductive adhesive130 applied to the pin connector 180 of an electrical device (not shown)electrically connected to a printed circuit board.

[0054] It is common to have connector housings for electrical deviceswith a plurality of electrical leads 60, 60′, etc. to make electricalconnections to conductive traces 181 on a printed circuit board.Electrical leads 60, 60′, etc. of the pin-type configuration (shown inFIGS. 10 and 11) are common in the personal computer (PC) industry andcan be found in almost every PC. An example of such a connector housing150 incorporating pin-type electrical leads 60, 60′, etc. is illustratedin FIG. 11. An external component such as a keyboard, printer, ormonitor is commonly connected to a central processing unit in thismanner. To protect such connectors from EOS transients, the presentinvention provides an electrical device comprised of a long hollowconductive tube 140 having an inner surface and an outer surface. A thinfilm of voltage variable material 10 is disposed on the outer surface ofthe tube 140. As shown in FIG. 12, the device is placed between a firstset of a plurality of electrical leads 60 and a second set of aplurality of electrical leads 60′. The outer thin film layer of voltagevariable material 10 is in electrical contact with both sets of leads60, 60′ and the inner surface of the conductive tube 140 is electricallygrounded.

[0055] Referring now to FIG. 13, the electrical device discussed abovewith respect to FIGS. 3-5 has a protective housing composed of a voltagevariable material 10.

[0056] Instead of an insulative, protective housing encapsulating a thinlayer of voltage variable material 10 physically connecting the leads60, 60′, etc. to the ground plane 70, the voltage variable material 10is molded around and encapsulates: a portion of the plurality ofelectrical leads 60, 60′, etc.; the ground plane 70; and the die or chiphaving electronic circuitry attached thereto 80. The exposed portions ofthe electrical leads 60, 60′, etc. are further formed into a desiredconfiguration (pin-style, flattened, etc.) to facilitate connection toanother electrical component.

[0057] In a further embodiment illustrated in FIG. 15, the housing 151of an electrical connector housing 150 is comprised of a voltagevariable material 10 to provide protection against EOS transients thatmay be applied to the electrical connectors 152.

[0058] While the specific embodiments have been illustrated anddescribed, numerous modifications come to mind without significantlydeparting from the spirit of the invention and the scope of protectionis only limited by the scope of the accompanying claims.

We claim:
 1. An electrical device for providing protection against EOStransients, the device comprising: a plurality of electrical leads, eachelectrical lead being spaced apart from the other electrical leads; aground plane adjacent to the plurality of electrical leads; a layer ofvoltage variable material filling the space between the plurality ofelectrical leads and physically connecting the plurality of electricalleads to the ground plane.
 2. The electrical device of claim 1 furtherincluding a die with a circuit integrated therein attached to the groundplane, each of the plurality of electrical leads being electricallyconnected to the integrated circuit by a conductive member.
 3. Theelectrical device of claim 1, wherein the spacing between each of theplurality of the electrical leads has a predetermined dimension, A, andthe spacing between each of the plurality of electrical leads and theground plane has a predetermined dimension, B, the dimension A beinggreater than the dimension B.
 4. The electrical device of claim 2,wherein the electrical leads, the ground plane and the die areencapsulated in a protective housing.
 5. The electrical device of claim4, wherein a portion of the electrical leads and a portion of the groundplane extend outwardly from the protective housing.
 6. A method formanufacturing an electrical device for providing protection against EOStransients, the method comprising the steps of: providing a lead framehaving a plurality of electrical leads and a ground plane, the leadframe having a predetermined spacing, A, between each electrical leadand a predetermined spacing, B, between each electrical lead and theground plane; applying a voltage variable material to the lead frame andphysically connecting the plurality of electrical leads to the groundplane, the voltage variable material filling the spacing, A, between theelectrical leads, and the spacing, B, between each electrical lead andthe ground plane; attaching a die having a circuit integrated therein tothe ground plane; electrically connecting the plurality of electricalleads to the integrated circuit; and trimming the plurality ofelectrical leads and the ground plane from the lead frame to form theelectrical device.
 7. The method of claim 6 wherein the step ofattaching a die having a circuit integrated therein is performed beforethe voltage variable material is applied to the lead frame.
 8. Themethod of claim 6 wherein the step of applying the voltage variablematerial to the lead frame includes laminating a thin film of EOSmaterial to the lead frame.
 9. The method of claim 6 further comprisingthe steps of: covering the electrical device with a protectiveinsulative coating such that a portion of the plurality of leads areexposed; and forming the exposed portions of the leads into connectorpins.
 10. An electrical device comprising: a layer of voltage variablematerial; a plurality of electrical leads disposed on the layer ofvoltage variable material; and a ground plane disposed on the layer ofvoltage variable material.
 11. A method for manufacturing an electricaldevice for providing protection against an EOS transient, the methodcomprising the steps of: providing a layer of voltage variable materialhaving a first and second surface; applying a first conductive layer tothe first surface of the voltage variable material and a secondconductive layer to the second surface of the voltage variable material;removing portions of the first conductive layer to form a plurality ofelectrical leads and a ground plane on the first surface of the voltagevariable material; and heating and applying pressure to the voltagevariable material such that the voltage variable material fills theremoved portions of the first conductive layer.
 12. An electrical devicefor providing protection against an EOS transient, the devicecomprising: a layer of voltage variable material having a first surfaceand a second surface; a first conductive layer disposed on the firstsurface of the voltage variable material, the first conductive layerelectrically grounded; first and second conductive terminal padsdisposed on the second surface of the voltage variable material; and adie having an electrical circuit integrated therein electricallyconnected to the first and second terminal pads.
 13. An electricaldevice for providing protection against EOS transients, the devicecomprising: a layer of voltage variable material having a first andsecond surface; a first conductive layer disposed on the first surfaceof the voltage variable material; a conductive adhesive disposed on thesecond surface of the voltage variable material, the conductive adhesivehaving an anisotropic voltage breakdown.
 14. The electrical device ofclaim 13 wherein the voltage breakdown of the conductive adhesivemeasured in a direction generally perpendicular to the layer of voltagevariable material is less than the voltage breakdown measured in anyother direction.
 15. An electrical device for providing protectionagainst an EOS transient, the device comprising: an electricallyinsulating substrate; a plurality of electrical leads disposed on thesubstrate; a ground plane disposed on the substrate; electricalcircuitry attached to the substrate and electrically connected to theplurality of electrical leads; and a layer of voltage variable materialdisposed on the substrate and contacting the plurality of electricalleads and the ground plane.
 16. The electrical device of claim 15wherein the electrical circuitry comprises a die having a circuitintegrated therein.
 17. The electrical device of claim 15 wherein theelectrical circuitry comprises a discrete electrical component.
 18. Anelectrical device for providing protection against EOS transients, thedevice comprising a hollow conductive tube having an inner surface andan outer surface, a layer of voltage variable material disposed on theouter surface of the conductive tube.
 19. An electrical device forproviding protection against EOS transients, the device comprising: aplurality of electrical leads, each electrical lead being spaced apartfrom the other electrical leads; a ground plane adjacent to theplurality of electrical leads; a die having a circuit integrated thereinattached to the ground plane; each of the plurality of electrical leadsbeing electrically connected to integrated circuit by a conductivemember; a housing composed of a voltage variable material encapsulatingthe plurality of electrical leads, the ground plane and the die, andphysically connecting the plurality of electrical leads to the groundplane; and a portion of each of the plurality of electrical leadsextending outwardly from the housing and forming a plurality ofconnector pins.